It's kind of a Hollywood cliche. Two beautiful people pretend to be two beautiful lovers and accidentally find themselves falling for each other in real life. Some blame the close (and isolated) quarters, some blame all the steamy kissing scenes. Whatever the reasons, it turns out that this stereotype exists for a good reason because actors are constantly falling hard and fast for their co-stars.

Naturally, when two co-stars hook up, the entire world knows about it. That goes double when the two actors play love interests onscreen. But every now and then, stars manage to keep their extracurricular activities under wraps long enough for speculation to blow over ... which is usually when they confirm their long-suspected romance to little fanfare. From Julia Roberts and Richard Gere to Chris Evans and Jessica Biel, here are 15 Movie Couples You Didn't Know Dated In Real Life.

15. Shia LaBeouf And Megan Fox In Transformers

Megan Fox and Shia LaBeouf in Transformers

This one was just a rumor for a long time, but Shia LaBeouf finally admitted it to be true. You could make the assumption that the claim was simply LaBeouf trying to look good, especially considering Megan Fox has never admitted to it herself. However, LaBeouf's comments on the relationship only confirm that it happened, leaving all details firmly out of the spotlight.

LaBeouf has been in relationships with many of his leading ladies, which is a habit he addressed in his confirmation of his relationship with Fox. LaBeouf pointed out that fans usually root for co-stars to end up together and that that will often lead to actors becoming romantically involved, especially when they are separated from the rest of the world for months with only each other as company.

 Jim Carrey And Renée Zellweger In Me, Myself, And Irene

Some couples you just don't see coming. Maybe Shia LaBeouf's explanation for his constant Hollywood hookups applies here, too? Despite seeming like they came from two different planets, Jim Carrey and Renée Zellweger fell for each other hard on the set of Me, Myself, And Irene.

The couple dated for 18 months and a very expensive ring was exchanged, but Carrey ultimately broke things off. While some rumors surmised that Carrey cooled on his feelings for Zellweger, and others alleged that he simply falls for his co-stars too quickly, a friend of Carrey's blamed his sudden rise to fame and an overabundance of media attention for coming between a relationship that seemed "perfect" to those who were close to the couple at that point in time.

 Josh Hutcherson And Vanessa Hudson In Journey 2: The Mysterious Island 

Obviously, any time teen stars appear in a movie together their rabid fans will be pulling for them to make their relationships official. Most of Josh Hutcherson's fans were likely rooting for him to hook up with his Hunger Games co-star, Jennifer Lawrence, but more on that later.

Hutcherson did have a habit of pairing off with his co-stars, including mega-teen-star Vanessa Hudgens who played his love interest in Journey 2: The Mysterious Island. Once again, the couple kept their relationship status a secret until after things were long over, awkwardly revealing their relationship (and subsequent breakup) in an interview. Though they've never revealed the reason for their tragic breakup, Hutcherson hinted on more than one occasion that Hudgens had "broken his heart" and that he was happy in the relationship.

 Ashton Kutcher And Brittany Murphy In Just Married

Sadly, Ashton Kutcher and Brittany Murphy were unable to fully recreate their onscreen love. Despite playing newlyweds in the aptly titled Just Married, Kutcher and Murphy never actually made it down the aisle ... but not for lack of trying.

The couple only dated for a few short months, but their interviews were peppered with hints of longterm relationship plans and they were spotted wearing matching rings. The rings were explained away as an homage to their couple status in the film. Kutcher's mother would go on record saying the couple was not engaged, though she was sure to poke at her son's acting performance, saying he behaved the same way around Murphy at home as he did in the movie. She also affirmed that she would have loved to see Murphy and Kutcher get married when they were ready. We're betting she badgered Mila Kunis over grandkids for months.

 Chris Evans And Jessica Biel In Multiple Films

How could this one have flown under so many radars? Sure, Jessica Biel and Justin Timberlake were a mega power couple for a while. And, yes, we absolutely adore Chris Evans and Jenny Slate together. But the world definitely should have been more hyped up about this, right?

Evans and Biel managed to slip their relationship of five years under the radar largely thanks to timing. Biel was still working on overcoming her squeaky clean 7th Heaven days and Evans was still years away from taking up Captain America's shield. The couple was so in love they lived together for a long time and talked about marriage more than once, but it simply wasn't meant to be.

10. Heath Ledger And Julia Stiles In 10 Things I Hate About You

Heath Ledger and Julia Stiles pointing in 10 Things I Hate About You.

What '90s kid didn't break their VHS tape of 10 Things I Hate About You after one too many rewinds frantically searching for clues of a real-life love connection between Heath Ledger and Julia Stiles? None, because we all did this. We had some solace when Stiles was linked to Joseph Gordon-Levitt, who played her fictional sister's love interest in the film. But that's really not the same thing, even a little bit.

Thankfully, after waiting a full decade to learn the truth, the 10-year anniversary DVD commentary of the film confirmed what we all knew to be true in our hearts: Heath Ledger and Julia Stiles were totally in love. There are still aren't a lot of details out there about this iconic relationship. Co-stars and crew simply confirmed the two fell in love while filming the movie, but that they broke up a year later. Some things really are too good to be true...

 9. Aubrey Plaza And Michael Cera In Scott Pilgrim Vs. The World

Julie Powers looks angrily at Scott in Scott Pilgrim vs the World

Not every secret Hollywood romance is shrouded in mystery. But when Aubrey Plaza dropped a bombshell on RuPaul's podcast, she let everything fly. When RuPaul admitted himself to be a major fan of Michael Cera's, Plaza revealed that she and Cera had dated for a year and a half back in the day.

RuPaul had put forth the theory that they had hooked up simply because they were working so closely in a somewhat isolated film set. However, Plaza squashed that idea quickly, saying that the young couple had really loved each other (and still do, as friends) and that they had once driven across the country to almost get married in Las Vegas. That's further than Julie ever got with her bitter, unrequited crush on Scott, at least.

 Cameron Diaz And Matt Dillon In There’s Something About Mary

Matt Dillon and Cameron Diaz's There's Something About Mary actually marked the end of their relationship rather than the beginning. While so many stars seem to make love connections while filming movies together, Diaz and Dillon dated three years before filming Mary and broke up not long after.

Dillon never proposed to Diaz, but he definitely thought about it. After their breakup, Dillon assured fans that he had been deeply in love with Diaz. But he had been considering marriage and kids very heavily and Diaz hadn't been ready to take that step. According to Dillon, his head-over-heels romance with Diaz had been his first real love and was his inspiration to grow and mature emotionally and romantically, causing him to seek more serious relationships after the split.

 Rooney Mara And Joaquin Phoenix In Mary Magdalene

This relationship should have had scandal written all over it, but was surprisingly lowkey considering the circumstances. Joaquin Phoenix and Rooney Mara were reportedly in love while co-starring in a film together. So far so normal. But Phoenix and Mara were busy filming Mary Magdalene, in which they portrayed Jesus Christ and Magdalene herself -- who you may recognize from The Bible and all the conspiracy theories linking them romantically.

Phoenix and Mara have been friends for a long time, but insider reports stated that after spending months alone in the desert filming the biblical epic, their platonic relationship began to blossom into something deeper. The actors denied the reports, saying they were simply good friends who had worked on many projects together over the years.

 Tom Cruise And Rebecca De Mornay In Risky Business

Viewers mocked Tom Cruise and Nicole Kidman's paltry attempts at steamy love scenes while filming Stanley Kubrick's Eyes Wide Shut. How could an actual married couple have such awful onscreen chemistry? Was there trouble at home? Was their real-life passion impossible to pick up on film? What exactly was going on?

As famous as he is for one of Hollywood's most lackluster love scenes ever, Cruise was also one half of one of the hottest films to date: Risky Business. It turns out, the fiery passion displayed in those scenes was totally real, if you believe rumors surrounding the movie. Cruise and co-star Rebecca De Mornay were swept up in a passionate affair during the time of filming, in spite of De Mornay's relationship with Harry Dean Stanton and Cruise's rumored revolving door of women coming in and out of his dressing room.

 Julia Roberts And Richard Gere In Pretty Woman

Richard Gere and Julia Roberts looking at each other at the races in Pretty Woman

It's often heralded as one of the most romantic films of all time, so, naturally, there had to be some real-life love stories playing out behind-the-scenes on the Pretty Woman film set, right? Again, nothing has ever been confirmed, but director Garry Marshall pretty much let the cat out of the bag on this one.

Marshall told The Huffington Post that Richard Gere had been more experienced and at ease during the kissing scenes and that he had been concerned with making Julia Roberts just as comfortable. But when pressed for answers over whether or not that easy going romance turned into more offstage, he quickly replied, "We don't talk about that!" Which seems to send an incredibly clear and obvious message that's difficult to deny.

 Michael Fassbender And Nicole Beharie In Shame

Pretty Woman may have been a movie about 'ladies of the night', but it was still a love story at heart. The same cannot be said for Michael Fassbender and Nicole Beharie's Shame. Fassbender and Beharie did play love interests in the film, it's just Fassbender's sex addict character likely had ... ulterior motives, to put things delicately.

Fassbender and Beharie didn't strike up a relationship until after filming was completed and they had hit the promotional circuit. The two then engaged in an incredibly long distance relationship with her in New York and him in England. As difficult as that distance must have been, we're actually not sure whether or not Fassbender's full-frontal nude scenes would have been easier or more awkward to film had they been dating during filming. Waiting was probably the right call here.

 Dove Cameron And Thomas Doherty In The Descendants 2

Alright, let's be real, any parent with a child between the ages of 8-15 knew about this one. Dove Cameron and Thomas Doherty's inescapable chemistry couldn't be avoided in its enthusiastic teen magazine coverage. These two land on the list thanks to their sweet ingenuity.

Cameron and Doherty's Descendants characters, Mal and Harry, never actually dated in canon, but the couple dreamed up a romantic (and tragic) backstory for their onscreen counterparts. According to Cameron, the pair decided their characters were each other's first loves who ultimately ended up suffering a painful breakup. They imagined themselves as wayward teenagers with "bad" attitudes and matching tattoos and would even take the time to draw their tats under their gloves while filming. These two are too cute for words.

 Jennifer Lawrence And Liam Hemsworth In The Hunger Games

Did Katniss choose Peeta or Gale in The Hunger Games? We won't spoil that for you (doesn't everyone know how this turned out by now?), but in the end, it doesn't matter, because Jennifer Lawrence definitely chose Liam Hemsworth over Josh Hutcherson in life.

Lawrence tends to take turns being both unapologetically blunt and incredibly secretive when it comes to clearing up rumors about her love life. But when Watch What Happens Live host, Andy Cohen, asked Lawrence whether or not rumors linking the two co-stars romantically were true, she very candidly revealed their private makeout sessions on the set of the Young Adult franchise. Lawrence maintained that she and Hemsworth had always been friends, but benefits were definitely involved from time to time.

Carrie Fisher And Harrison Ford In Star Wars

Everyone knew about this one. Everyone at least suspected it. And yet, Carrie Fisher and Harrison Ford managed to keep their torrid affair on the Star Wars set a secret for four decades. Their hot and heavy romance was confirmed when Fisher decided to drop that bomb herself in her own memoir, because Fisher was queen.

Fisher reached out to Ford to get the go-ahead to publish her diaries and expressed empathy for his fiercely private sensibilities. Which served as a nice way of bringing their relationship full circle, as Fisher had applauded Ford's ability to incite trust during their time together. Fans were both ecstatic and upset by the revelation, given their ages at the time (33 and 19) and Ford's married status. But Fisher squashed that with her signature brashness saying, "What happens on location, is permitted." Fair, enough.

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Which one of these surprised you most? Let us know in the comments!